642-889 Latest Exam (Aug 2018)

[Free] 2018(Aug) Dumps4cert Cisco 642-889 Dumps with VCE and PDF Download 41-50

August 19, 2018

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Implementing Cisco Service Provider Next-Generation Egde Network Services

Question No: 41

Whenis it appropriate to activate the VPNv6 address family?

  1. when implementing 6PE

  2. when running dual stack at the provider edge

  3. when implementing 6to4 tunneling

  4. when implementing 6VPE

Answer: D

Question No: 42

Which VPN technology is an example of a full-mesh VPN?

  1. VTI

  2. GRE VPN

  3. Frame Relay L2 VPN


Answer: D

Question No: 43

Which option represents an AToM pseudowire basic configuration in Cisco IOS XR device?

  1. pseudowire-class name_class encapsulation mpls


  2. pseudowire-class name_class encapsulation l2tpv3


  3. l2vpn pw-class name encapsulation mpls


  4. l2vpn xconnect group group-name p2p xconnect-name

  5. neighbor ip-address pw-id pseudowire-id

Answer: C

Question No: 44

With Layer 3 MPLS VPN implementations on Cisco IOS XR PE routers, an interface is assigned to a VRF using the vrf command in which configuration mode?

  1. RP/0/RP0/CPU0:PE(config-vrf)#

  2. RP/0/RP0/CPU0:PE(config-if)#

  3. RP/0/RP0/CPU0:PE(config-bgp)#

  4. RP/0/RP0/CPU0:PE(config-bgp-af)#

Answer: B

Question No: 45

In MPLS Layer 3 VPN implementations, what is used at the PEs to transform the customer IPv4 prefixes into a unique 96-bit prefix?

  1. RT

  2. RD

  3. VC ID

  4. PW ID

  5. AS number

Answer: B

Question No: 46

An engineer is deploying L2VPN service between two different Layer 2 encapsulations. Which feature should be set up to accomplish this task?

  1. interworking VLAN on both the provider edge routers

  2. interworking Ethernet on both the provider edge routers with VLAN tagging

  3. interworking IPv4 on both the customer edge routers

  4. interworking IPv4 on both the provider edge routers

Answer: D

Question No: 47

O: 121

Refer to the exhibit.

Dumps4Cert 2018 PDF and VCE

PE1 and PE2 are advertising the same subnet to PE3. Which PE advertised subnet is installed at PE3 BGP table?

  1. PE2 subnet only due to the same RD value with PE1

  2. PE2 subnet only due to the same RD value with PE3

  3. Both PE1 and PE2 subnets due to exported subnet with RT matches import RT on PE3

  4. PE1 subnet only due to exported subnet with RT matches import RT on PE3

Answer: D

Question No: 48

Whichthree possible misconfigurations can occur on the backbone IGP section of an MPLS Layer 3 VPN setup? (Choose three.)

  1. configuring the LDP router ID with an incorrect loopback interface

  2. configuring the wrong AS number on a client eBGP peering

  3. configuring the wrong area number on a PE-CE OSPF link

  4. decreasing the MPLS MTU

  5. disabling MPLS on a core link

  6. disabling MPLS LDP sync in the IGP routing process

Answer: A,D,E

Question No: 49

Which three Layer 3 VPN technologies are based on the overlay model? (Choose three.)

  1. ATM virtual circuits

  2. Frame Relay virtual circuits

  3. GRE/IPsec

  4. L2TPv3

  5. MPLS Layer 3 VPNs

  6. DMVPNs

Answer: C,D,F Explanation:

The overlay model, where the service provider provides emulated leased lines to the customer.

The service provider provides the customer with a set of emulated leased lines. These leased lines are called VCs, which can be either constantly available (PVCs) or established on demand (SVCs). The QoS guarantees in the overlay VPN model usually are expressed in terms of bandwidth guaranteed on a certain VC (Committed Information Rate or CIR) and maximum bandwidth available on a certain VC (Peak Information Rate or PIR). The committed bandwidth guarantee usually is provided through the statistical nature of the Layer 2 service but depends on the overbooking strategy of the service provider The peer- to-peer model, where the service provider and the customer exchange Layer 3 routing information and the provider relays the data between the customer sites on the optimum path between the sites and without the customer#39;s involvement.

The peer-to-peer VPN model was introduced a few years ago to alleviate the drawbacks of the overlay VPN model. In the peer-to-peer model, the Provider Edge (PE) device is a router (PE-router) that directly exchanges routing information with the CPE router. The Managed Network service offered by many service providers, where the service provider also manages the CPE devices, is not relevant to this discussion because it#39;s only a repackaging of another service. The Managed Network provider concurrently assumes the role of the VPN service provider providing the VPN infrastructure) and part of the VPN customer role (managing the CPE device).

The peer-to-peer model provides a number of advantages over the traditional overlay model:

Routing (from the customer#39;s perspective) becomes exceedingly simple, as the customer router exchanges routing information with only one (or a few) PE-router, whereas in the overlay VPN network, the number of neighbor routers can grow to a large number.

Routing between the customer sites is always optimal, as the provider routers know the customer#39;s network topology and can thus establish optimum inter-site routing.

Bandwidth provisioning is simpler because the customer has to specify only the inbound and outbound bandwidths for each site (Committed Access Rate [CAR] and Committed Delivery Rate [CDR]) and not the exact site-to-site traffic profile.

The addition of a new site is simpler because the service provider provisions only an additional site and changes the configuration on the attached PE-router. Under the overlay VPN model, the service provider must provision a whole set of VCs leading from that site to other sites of the customer VPN.

Prior to an MPLS-based VPN implementation, two implementation options existed for the peer-to-peer VPN model:

The shared-router approach, where several VPN customers share the same PE-router. The dedicated-router approach, where each VPN customer has dedicated PE-routers.

Question No: 50

Within the service provider IP/MPLS core network, what must be implemented to enable Layer 3 MPLS VPN services?

  1. IS-IS or OSPF on all the PE and P routers

  2. MP-BGP between the PE routers

  3. RSVP on all the PE and P routers

  4. targeted LDP between the PE routers

  5. LDP between the CE and PE routers

Answer: B

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